They said he preached that they should not circumcise their children and should not walk according to the customs, that is, should not fulfill the rites of the law of Moses.
These are evidently the same opponents of Paul, the teachers who troubled the Church of Antioch and Jerusalem. They demanded circumcision and observance of the law of Moses even for Gentiles turning to Christ (ch. 15).
The accusation against Paul, released among the people, was slander. From all his teaching, as it is unfolded in his epistles, and from all his activity, one sees what alone he taught.
He taught that the salvation of those who believe in Christ is conditioned neither by circumcision nor by fulfillment of the law of Moses, but by faith in Christ Jesus. See the Epistles to the Romans, Galatians, and Corinthians.
This means: if you wish, keep the law of Moses; if you wish, do not. His act concerning circumcision bears witness to how he taught about it. Taking Timothy as his fellow worker, he circumcised him.
Thus the insinuation that Paul was an apostate from the law and taught others apostasy was a malicious insinuation and slander against the Apostle.”